This invention relates to a method for laser texturing a substrate.
A typical process for manufacturing a magnetic disk comprises the following steps:
1. An Al alloy substrate is plated with an 8 .mu.m thick NiP layer. PA0 2. The NiP is laser textured, e.g., as discussed in U.S. Pat. No. 5,062,021 and 5,108,781, issued to Ranjan et al., incorporated by reference. PA0 3. An underlayer, magnetic layer and protective overcoat are sputtered onto the textured NiP layer. (The underlayer is typically Cr, the Magnetic layer is typically a Co alloy and the protective overcoat is typically a hydrogenated carbon overcoat.)
The laser texturing step is performed because a texture on a magnetic disk has the beneficial effect of reducing stiction and friction between a read-write head and the disk during CSS ("contact start stop") operation.
It is also known in the art to use substrate materials other than Al. For example, it is known to use glass and glass ceramic. U.S. patent application Ser. No, 08/657,222, filed by C. Ross, discusses using glass substrates. Teng et al., "Laser Zone Texture on Alternative Substrate Disks", IEEE Trans. on Magnetics, Vol. 32, No. 5 (September 1996), pp. 3759-3761 discusses glass ceramic substrates. Teng and Ross are incorporated herein by reference. The advantage of glass or glass ceramic substrates is that they are extremely hard, and unlikely to sustain damage caused by impact with a read-write head.
The above-mentioned Teng paper discusses laser texturing glass ceramic substrates with a CO.sub.2 laser. Teng's FIG. 5b shows that he was able to produce a smooth bump about 30 nm high and about 15 to 20 .mu.m wide with a CO.sub.2 laser.
As flying heights decrease, and read-write heads become smaller, it will be desirable to be able to form extremely small texture features on a magnetic disk. In the past, there has been a limit to the size of the texture features one can form with a laser only process.